Changes in snuff and smoking habits in Swedish pregnant women and risk for small for gestational age births
Correspondence: S Baba, Department of Medicine, Clinical Epidemiology Unit, Karolinska Institutet, SE-171 76 Stockholm, Sweden. Email Sachiko.firstname.lastname@example.org
To examine associations between antenatal exposure to Swedish oral moist snuff (which includes essentially only nicotine) and to smoking and risks of small-for-gestational-age (SGA) births and to compare risks among women who stopped or continued using snuff or smoking during pregnancy.
Population-based cohort study.
All live singleton births in Sweden 1999–2010.
Odds ratios (OR) with 95% confidence intervals (CI) were calculated using multiple logistic regression analysis.
Main outcome measures
SGA birth, also stratified into preterm (≤36 weeks of gestation) and term (≥37 weeks of gestation) SGA births.
Compared with non-tobacco users in early pregnancy, snuff users and above all smokers in early pregnancy had increased risks of SGA births: adjusted ORs (95% CI) were 1.26 (1.09–1.46) and 2.55 (2.43–2.67), respectively). Snuff use had, if anything, a stronger association with preterm SGA than term SGA, whereas the opposite was true for smoking. Compared with non-tobacco users, women who stopped using snuff before their first visit to antenatal care had no increased risks of preterm or term SGA, and women who stopped using snuff later during pregnancy had no increased risk of term SGA. Smoking cessation early in pregnancy was associated with a larger reduction in risk than smoking cessation later in pregnancy.
As both smoking and snuff use influence risk of SGA, both nicotine but above all tobacco combustion products are involved in the mechanisms by which maternal smoking increases the risk of SGA.